Create an interactive drawing program.
When a mouse button is pressed, or the mouse is moved with the button pressed, draw something at the location of the mouse. Preferably, a continuous stroke should be drawn as the mouse moves.
Allow the user to change the color being drawn. A minimal interface would be: hit "r" key to draw in red, "g" to draw in green, "b" to draw in blue.
Due: in class, Thursday, September 18.
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| Vannevar Bush - MEMEX |
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| Ivan Sutherland - Sketchpad |
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| MIT - Spacewar |
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| Ivan Sutherland - Ultimate Display |
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| Douglas Engelbart - NLS (oNLine System) |
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| Xerox PARC - Star |
Change in response to users' actions
Lets users know that they're interacting
Immediate, simple response often useful
Can be visual, auditory, haptic
Delay between an action and its result
Humans very aware of latency > ~ 100 milliseconds
Many delays inherent in different stages of hardware/software
"End-to-end" latency = total delay
Long latency slows up user
Irregular latency even worse
Latency is distinct from update speed
Measure of how many distinct values a device can report
On/off switch = 1 bit resolution
"Non-analog" joystick = 3 values (+1, 0, -1) for X and for Y
8 bit resolution joystick = 256 possible values for X and for Y
16 bit resolution joystick = 65536 possible values for X and for Y
Signal = the information we want to communicate to the computer (e.g. button state, pointer position)
Noise = variations in the signal, outside of our control
Examples:
Applications may need to allow for noise in input data
From human movement research - Paul Fitts, 1954
Predicts time needed to move from a starting position to a target - e.g. to point at something
D = distance to target
W = width of target
| glutKeyboardFunc(func) | Called when a 'character' key is hit |
| glutSpecialFunc(func) | Called when a 'special' key is hit |
| glutKeyboardUpFunc(func) | Called when a 'character' key is released |
| glutSpecialUpFunc(func) | Called when a 'special' key is released |
| glutGetModifiers() | Returns state of shift, control, alt keys when event happened |
| glutIgnoreKeyRepeat(val) | Tells GLUT whether to ignore automatic keyboard repeat |
All keyboard callback functions take the form:
def func(key, x, y):
...
key is the key pressed or released - either a single-character string (e.g. 'a'), or a special-key constant (e.g. GLUT_KEY_UP)
x, y is the mouse pointer location when the key event occurred
| glutMouseFunc(func) | Called when a mouse button is pressed |
| glutMotionFunc(func) | Called when mouse moves, while button pressed |
| glutPassiveMotionFunc(func) | Called when mouse moves, with no button pressed |
| glutGetModifiers() | Returns state of shift, control, alt keys when event happened |
Mouse-button callback functions take the form:
def func(button, state, x, y):
...
button is the button pressed or released - one of GLUT_LEFT_BUTTON, GLUT_MIDDLE_BUTTON, or GLUT_RIGHT_BUTTON
state is GLUT_DOWN if the button was pressed, or GLUT_UP if it was released
x, y is the mouse pointer location when the button was pressed or released
Mouse-motion callback functions take the form:
def func(x, y):
...
x, y is the new mouse pointer location
Mouse positions are given in window coordinates
Measured in pixels, from the upper left corner
